Porcine circovirus (PCV) was originally identified as a contaminant of porcine kidney cell cultures (PK15 ATCC CCL-33). The PCV virion has been characterized as being an icosahedral, non-enveloped virus with a single-stranded circular DNA of about 1.76 kb. PCV was classified in the genus Circovirus of the Circoviridae family, which consists of other animal circoviruses such as psittacine beak-feather disease virus, goose circovirus, canary circovirus, and pigeon circovirus. Two genotypes of PCV have been recognized. The PK15 cell-derived PCV has been considered to be nonpathogenic to pigs, and is designated PCV type 1 (PCV1). On the other hand PCV type 2 (PCV2) has been accepted as the major infectious agent involved in several pigs diseases. PCV2 associated diseases cause significant economic losses to swine producers worldwide. A review of PCV2 associated infections have been well described in the patent WO2007/076520 and include for example Postweaning Multisystemic Wasting Syndrome (PMWS), Porcine Dermatitis and Nephropathy Syndrome (PDNS), Porcine Respiratory Disease Complex (PRDC), reproductive disorders, granulomatous enteris, exsudative epidermitis, necrotizing lymphadenitis, and congenital tremors. Occurrences of PCV2 subtype A (PCV2A) and PCV2 subtype B (PCV2B) have been reported particularly in 2000 in West Europe and in Central Europe in 2003. More recently similar changes have been reported in 2008 in wild boars.
Currently developed PCV2 vaccines such as CIRCOVAC (Merial), INGELVAC CircoFLEX (Boehringer Ingelheim Vetmedica), SUVAXYN PCV2 (Fort Dodge), are based on inactivated PCV2A, or on the expression of ORF2 gene of PCV2A by a baculovirus vector. It is thus necessary to develop PCV2 vaccines that would be broadly effective against all PCV2 associated diseases. However, current PCV2 strains subtype A or B present several weaknesses. Particularly, PCV2 viruses can only be produced at low titres, generally less than 105 TCID50 viral particles per mL. Also, these viruses cannot be maintained in tissue cultures and permanently infected cell lines. The Applicant has discovered a novel PCV2 isolate belonging to subtype B which can address the issues of PCV2 vaccines as developed so far, such as high titre growth and maintenance of PCV2 in tissue culture.